As is commonly known, quartz crystals are used to control the frequency of electrical oscillators and in other circuits where an electrical resonant frequency is used. However, a problem with such crystals is that their natural resonant frequency changes with acceleration that may be applied to the crystal. The deleterious effects of such acceleration induced frequency shifts are well known by the designers of systems that require high precision frequency control.
One method of minimizing the acceleration induced frequency shifts is discussed in U.S. Pat. No. 4,344,010. In that application, it is shown that acceleration resistant resonators can be obtained by providing two crystals which are electrically coupled or mechanically coupled, or both electrically and mechanically coupled together. U.S. Pat. No. 4,344,010 further discloses that the acceleration sensitivity can be minimized by the use of two resonators, one of which is left-handed, and the other of which is right-handed; the crystallographic axes of which are aligned antiparallel.
Although the method of U.S. Pat. No. 4,344,010 minimizes the acceleration induced frequency shifts, implementation of the method as disclosed in U.S. Pat. No. 4,344,010 is complicated in that it requires two separate pieces of quartz that have to be individually fabricated in such a way that properties such as crystallographic orientation have to be properly matched. Moreover, the pieces in U.S. Pat. No. 4,344,010 are required to be aligned and mechanically joined together subsequent to fabrication.